From the late-1940s through the mid-1970s, the demand for ion exchange resins grew by high single digits. However, by the mid-1970s, polymeric membranes had eclipsed ion exchange in growth rates, causing the growth of ion exchange technology to decline to low single digits. This was strongly influenced by the more aggressive growth of Reverse Osmosis (RO) and partially catalyzed by RO companies promoting the lack of a third stream of regenerant chemicals causing more pollution. Thus, RO became a billion dollar industry with global acceptance as the best value. However, this growth generated awareness of new issues, including that of the concentrates or rejects from RO being discharged into the ocean at double the feed salinity. RO companies who used to claim an advantage over ion exchange because they did not generate a third regenerant chemical stream thus found the new issue of what to do about their second stream and the carbon foot print.
Moreover, the growth of RO technology diverted research and development of other water treatment technologies, notably Forward Osmosis (FO) and Nanofiltration (NF) technologies. As such, presently, over eighty percent of the world's desalination capacity is based on RO technology. Substantial investments of capital, engineering and marketing provided the foundation for this rapid and widespread growth. In addition to affording the basic chemistry and material science research, these investments further conferred development of precise, automated and reliable manufacturing processes and equipment as well as associated analytical, modeling and optimal design software technologies.
However, physical and technical limits to the applicability and performance of RO has inhibited performance gains as RO technology has matured. In this regard, various impediments limit future performance advances of the technology. For example, though increases in the percentage of freshwater recovery (permeate) are desirable, with conventional RO technology alone, in high salinity waters, the recovery tends to top out at about 42% (with about 58% reject/concentrate) at salinities of approximately 65,000 parts per million (ppm), which approaches a thermodynamic limit of 45% recovery (55% reject/concentrate) or 1.8 cycles of concentration at similar salinities.
If the status quo is maintained with respect to seawater desalination process technology, by 2030, 65 billion gallons per day (23 trillion gallons per year) of high salinity (>65,000 ppm TDS) discharge will find its way to the oceans. Without adjacent space process technologies to flank SWRO membranes, the thermodynamic factor is an anchor as is the limiting inflection point of the ‘S’ curve of RO membranes, a product that cannot be much improved as it is already at or near its peak performance. Moreover, concern over the lack of environment friendly options and ever rising volume and salinity continues to grow. Additionally, existing zero liquid discharge technologies of evaporation and crystallization are typically too expensive to be practical.
Accordingly, systems and methods which can increase the recovery rate of fresh water from otherwise undesirable water, as well as provide additional uses for the by-products and/or wastewater of such systems and methods are desirable. The present disclosure addresses these needs and other limitations of the prior art.